As the levels of integration within semiconductor devices increase, the wiring layers continue to become increasingly miniaturized. However, in these very fine wiring layers, the effects of signal delays within the wiring layer tend to increase, impeding increases in the signal transmission speed.
These signal delays are proportional to the resistance of the wiring layer and the capacity between wiring layers, and therefore in order to achieve higher transmission speeds, the resistance of the wiring layers and the capacity between wiring layers must be reduced.
Accordingly, in recent years there has been a change in the materials used in forming the wiring layers, from the more conventional aluminum to low resistivity copper, whereas interlayer insulating films having a low dielectric constant are now being used to reduce the capacity between wiring layers.
For example, an SiO2 film has a dielectric constant of 4.1 and an SiOF film has a dielectric constant of 3.7, but recently, SiOCH films and organic films having even lower dielectric constants are starting to be used.
In this manner, the dielectric constant of interlayer insulating films continues to decrease gradually, and much research is being conducted into the development of low dielectric constant interlayer insulating films having a dielectric constant of 2.4 or lower for next generation applications. Interlayer insulating films for which the dielectric constant is less than 2.0 have also been reported recently.
Further, in multilayer wiring structures that use copper for the wiring layers, an insulating film having a copper diffusion barrier property is inserted at each interface between a copper wiring layer and an insulating film in order to prevent diffusion of the copper into the insulating film.
An insulating film composed of silicon nitride or SiCN or the like, which exhibit superior copper diffusion barrier properties, is typically used for this copper diffusion barrier insulating film, but such films have a high dielectric constant of 4 to 7, which increases the effective dielectric constant of the overall insulating film that constitutes the multilayer wiring structure.
For example, in a multilayer wiring structure in which an interlayer insulating film having a dielectric constant of approximately 2.5 is laminated to a copper diffusion barrier insulating film having a dielectric constant of approximately 4, the effective dielectric constant is approximately 3.
In other words, in order to lower the effective dielectric constant, a reduction in the dielectric constant of the copper diffusion barrier insulating film is required, and considerable research and development aimed at achieving that goal is currently in progress.
Previously, a copper diffusion barrier insulating film which uses an organosilane material having π-electron bonds and is composed mainly of silicon and carbon has been reported (see Patent Document 1).
[Patent Document 1]
Japanese Unexamined Patent Application, First Publication No. 2005-45058